PROJECT SUMMARY ABSTRACT Imbalance of the 2 essential vitamins folate and vitamin B-12 is associated with negative health outcomes such as anemia cognitive dysfunction in older adults. Folate and vitamin B-12 play central roles in one carbon metabolic pathway, which generates precursors for nucleotide biosynthesis and methyl groups for methylation reactions. While adequate folate nutrition is necessary for optimal health, consumption of excess from supplements and fortified foods has been associated with adverse health outcomes in a segment of the population who are at risk for vitamin B-12 (cobalamin) deficiency. The elderly are particularly vulnerable to this interaction, since absorption of vitamin B-12 from diet decreases with age due to gastric atrophy and antacid use and consumption of folic acid containing supplements is highly prevalent among the elderly. The importance of this health concern is reflected in the recent report of the US National Toxicology Program that recommended additional research on the adverse effects of excess folic acid consumption on cognition and the mechanism behind the interaction with vitamin B-12 status which is currently not known. Prior to taking steps to address this public health issue, it is necessary to establish a cause-effect relationship between the B vitamin imbalance and adverse outcomes and to determine the mechanism behind this interaction. To accomplish this, a non-human model for this interaction is necessary for ethical reasons. A rodent model for this interaction has not been successful, despite efforts by multiple labs. In the project proposed in this R03 application, we propose to develop a Caenorhabditis elegans model of this interaction. C. elegans is a highly time and cost effective model due to its short life cycle, life span and ease of genetic manipulation. For 60-80% of human genes (depending on the bioinformatics approach) homologs have been identified in C. elegans and it is a viable model to study aging, the nervous system, learning and memory. Vitamin B-12 deficient C. elegans will be generated by feeding them a diet of E. coli grown on vitamin B-12 deficient media over multiple generations. We will test 3 folate forms that are used as supplements in humans. To study high folate/low vitamin B-12 interaction, C. elegans will be fed folic acid, methyl folate or folinic acid at different concentrations provided on the top of live or heat-killed bacterial lawn. Specific Aims of this project are 1). To demonstrate worsening of metabolic vitamin B-12 deficiency with a high folate diet in C. elegans. 2). To determine the effect of imbalance of high folate /low vitamin B12 nutrition on life cycle, life span and memory of C. elegans. If this project is successful, this model will be used to understand the mechanism behind the adverse interaction of high folate and low vitamin B-12 status in future studies.